avoiding a tiled looking ocean simulation
If you aren't going to see the ocean very close up, I wouldn't use the ocean modifier for this at all.

Instead you can probably get a reasonable result using a simple plane and some bump-mapping:





See How can I create a convincing sea material in Cycles without using the ocean modifier? for more details.



That said, if you still want to use the ocean modifier, you could try adding multiple displace ocean modifiers with different settings after the initial modifier.

Try varying settings like the time  and spatial size between modifiers.

Here's an example with three displace ocean modifiers after a generate ocean modifier, each with different a time and spatial size: